Photographic processes are being used to a great extent today. Typical of an industrial use is the large amount of X-ray film sold and processed each year. Essential to a photographic process is the use of silver compounds; and, in particular, silver halides. The silver compounds are dissolved throughout an emulsion, which is deposited upon a photographic film or plate. During development of the photographic film, silver is removed from unexposed or under-exposed areas of the film by the development process.
A developer, a stop bath, and a fixer acquire silver from the film as a result of the development process. When the developer, the stop bath or the fixer are exhausted, they are usually disposed of by pouring down a drain of a sink. Any silver dissolved in these photographic chemicals is, of course, also poured down the drain and wasted. Silver is becoming increasingly expensive; and large amounts of silver are used each year by the photographic industry.
In addition, heavy metals (such as silver) which are disposed of by pouring down a drain present a pollution hazard. The metals disposed of in this manner can be ingested by organisms and poison them.
Devices have been developed for removing silver from photographic chemicals. The devices previously developed cannot handle large amounts of liquid on a continuous basis. Furthermore, these devices often have a tendency to burn the photographic chemicals through the application of excessive electroplating currents.
What is needed is a device or method which is automatic; and should be able to quickly and conveniently remove the silver or other metals from the solution in which they are found and dispose of the exhausted solution after the metal has been removed. The device or method should be able to handle large amounts of liquid on a continuous basis; and should not burn the liquid being treated.